The present invention relates to a manufacturing method and manufacturing equipment of a flat panel display, which has an electron emitting element, such as a field emission cold cathode or the like.
Recently, by making use of highly developed semiconductor machining techniques, a field emission cold cathode is under active development, and an application of the field emission cold cathode to a flat panel (planar type) display is under progress. A flat panel display having a filed emission type electron-emitting element is self-emitting type, different from a liquid crystal display, and a backlight is unnecessary. Accordingly, there are various advantages that low power consumption may be realized, a broader field angle may be obtained, and a rapid response speed may be obtained.
As the flat panel display like this, one that has a structure, such as shown in FIGS. 7A and 7B, is known. FIG. 7B is a sectional view showing, in enlargement, a portion surrounded by a circle in FIG. 7A.
In this image display, a silicon dioxide film 103, which has a large number of cavities 102, is formed on a Si substrate 101 as a rear plate, and, a gate electrode 104, consisting of molybdenum or niobium, is formed on the silicon dioxide film 103. A field emission type electron emitting element 105, consisting of cone-like molybdenum or the like, is formed on the Si substrate 101 inside the cavities 102.
A transparent substrate (face plate) 106, consisting of a glass substrate or the like, is disposed in parallel with the Si substrate 101 like this, which has a large number of electron emitting elements 105, so as to face the Si substrate 101 with a predetermined spacing. Therefrom, a vacuum envelope 107 is configured. A phosphor screen 108 is formed on a surface facing the electron emitting elements 105 of the transparent substrate 106. In addition, in order to sustain an atmospheric pressure on the Si substrate 101 and the transparent substrate 106, supporting members 109 are disposed between these substrates.
In the aforementioned flat panel display, electron beams, emitted from a large number of electron emitting elements 105, are illuminated on the phosphor screen 108; the phosphor screen 108 is excited to emit light; and, thereby, an image is formed. In the image display like this, the electron emitting elements 105 may be formed in a small size of micrometer-order, and the spacing between the Si substrate 101 and the transparent substrate 106 may be formed in a size of millimeter-order. As a result, in the flat panel display, higher resolution, lighter weight, and thinner thickness may be attained, in comparison with cathode ray tubes (CRT) which have been used for television sets or computer displays.
In the flat panel display having the aforementioned structure, a vacuum degree inside the device is necessary to be maintained in the range of, for instance, 10xe2x88x927 to 10xe2x88x928 Torr. In order to attain this, in the existing exhausting process, gas adsorbed on an inside surface of the image display is degassed in the shortest time, by applying baking treatment, in which the image display is heated up to approximately 350xc2x0 C. However, by such an exhausting method, the gas adsorbed on the surface cannot be sufficiently degassed.
On the other hand, in the existing CRTs and so on, a getter disposed inside the device is activated after sealing, and, the gas released from an inner wall, during operation, is absorbed by the getter, thereby a desired degree of vacuum is maintained. This technique for obtaining a high vacuum and maintaining a A degree of vacuum by means of gettering material is under way in applying in the flat panel displays.
In the flat panel display in which the field emission electron emitting elements are used, while a volume of a vacuum vessel (vacuum envelope), which is determined by the rear and face plates and the supporting frame disposed at the sides thereof, may be largely reduced in comparison with that of the ordinary CRT, an area of an inner surface, from which the gas is released, is not so much reduced. As a result, when the surface adsorption gas is released to an extent equivalent with that of the CRT, an increase in pressure in the vacuum vessel becomes remarkably large. Accordingly, in the flat panel display, role of the gettering material becomes very important. However, a place, where a conductive gettering film is formed, has been limited, from a viewpoint of inhibiting short circuits of interconnections.
To such problems, it is proposed to dispose the gettering material at a position, other than an image display region, of the vacuum vessel, and to form the gettering film, in a periphery portion that does not affect on the image display region (Japanese Patent Laid-Open Application No. 5-151916 JP-A, Japanese Patent Laid-Open Application No. 4-289640 JP-A, and so on). However, according to such methods, the gas generated in the image display region may not be effectively absorbed by the gettering film, which is formed in the periphery portion. As a result, there has been a problem that it is difficult to maintain a high vacuum in the vacuum envelope, over a long time period.
By the above reasons, it is under study to dispose the gettering film in the image display region. In Japanese Patent Laid-open Application No. 9-82245 JP-A, for instance, the following is disclosed. That is, a gettering material, consisting of titanium (Ti), zirconium (Zr), or alloy thereof, is sputtered on a metal back layer, which is formed on a phosphor film in a faceplate of a flat panel display; or the metal back hd layer is constituted of the aforementioned gettering material; or the above gettering material is disposed on a portion, other than the electron emitting element, of the rear plate, in the image display region.
However, in the flat panel display, which is disclosed in the above Japanese Patent Laid-Open Application No. 9-82245 JP-A, since the gettering material is formed according to an ordinary panel formation process, a surface of the gettering material is naturally oxidized. In the gettering material, since activity of the surface thereof is very important, the surface-oxidized gettering material could not obtain a sufficient gas absorption effect.
Therefore, in the above publication, it is disclosed that, after a space between the faceplate and the rear plate is hermetically sealed through supporting frames, and a vacuum envelope is formed, the gettering material is activated by means of electron beam irradiation and so on. However, according to such method, the gettering material may not be effectively activated. In particular, in case the gettering material is activated, after the vacuum envelope is formed, since gas components, such as oxygen or the like, which are released due to the activation, are adsorbed by the electron emitting elements or other members, electron emissivity or the like may be deteriorated.
The present invention is carried out to overcome these problems. The object of the present invention is to provide a method for manufacturing a flat panel display, according to which, gas adsorbed on an inside surface of the device in the course of manufacturing process, may be sufficiently degassed, and, thereby, a high vacuum state may be maintained inside the vacuum vessel (the vacuum envelope); and manufacturing equipment of the flat panel displays.
A first aspect of the present invention is a manufacturing method of a flat panel display. The manufacturing method of a flat panel display comprises joining a substrate, which has an electron emitting element, and a faceplate, which has a phosphor screen, so that the electron emitting element and the phosphor screen face to each other with a gap and irradiating electrons onto at least one of the substrate and the faceplate, in a vacuum atmosphere.
More specifically, the irradiating of electrons has accommodating at least one of the substrate and the faceplate in a treatment vessel, and irradiating the electrons onto at least one of the substrate and the faceplate accommodated in the treatment vessel from one or more electron sources disposed therein.
In the present manufacturing method of the flat panel display, the electrons are preferably irradiated in a vacuum atmosphere of which degree of vacuum is maintained at 10xe2x88x923 Torr or less in the irradiating of electrons. In addition, in the electron irradiating process, it is preferable to irradiate the electrons onto at least one of the substrate and the faceplate, while being heated. In heating, at least one of the substrate and the faceplate is preferably heated to a temperature from 200 to 400xc2x0 C. Furthermore, after the electrons are irradiated, an irradiated object is preferably cooled to a temperature of 100xc2x0 C. or less. After the irradiating of electrons, the substrate and the faceplate may be joined through a supporting frame in a vacuum atmosphere. The supporting frame may be irradiated with the electrons.
A second aspect of the present invention is a manufacturing equipment of a flat panel display. The manufacturing equipment of a flat panel display comprises a treatment vessel in which at least one of a substrate, which has an electron emitting element, and a faceplate, which has a phosphor screen, is accommodated, transferring means for sending at least one of the substrate and the faceplate in and out of the treatment vessel, exhausting means for evacuating the inside of the treatment vessel to a vacuum atmosphere, irradiating means for irradiating an electron beam onto at least one of the substrate and the faceplate, which are accommodated in the treatment vessel, and joining means for joining the substrate and the faceplate, at least one of which is irradiated with the electron beam, while arranging so as for the electron emitting element and the phosphor screen to face to each other with a gap.
The manufacturing equipment of a flat panel display of the present invention may further include means for heating at least one of the substrate and the faceplate, which are accommodated in the treatment vessel.
In general, the irradiation of the electron beam onto a solid material may detach gas adsorbed on a solid surface. Accordingly, by accommodating the substrate, which has the electron emitting elements, or the faceplate, in the treatment vessel, the inside of which is evacuated to be a vacuum atmosphere, and by irradiating the electron beam onto the substrate or the faceplate, from an electron source disposed in the treatment vessel, an entire surface of the substrate and of the faceplate may undergoes thorough electron beam cleaning, and, thereby, surface adsorbed gas may be sufficiently released. By performing such electron beam irradiation, the inside of the vacuum vessel, which constitutes the envelope of the flat panel display, may be made capable of maintaining a high vacuum state, for instance, a degree of vacuum of from 10xe2x88x927 to 10xe2x88x928 Torr.